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Explain why the driver of a car has to continuously apply pressure to the gas pedal in order to keep the car cruising at a steady speed, even on a flat road.

1 Answer
Andrea B.
Mar 11, 2018

see below

Explanation:

You have mainly two friction forces:
1) a friction between the tire and the road: this friction force is proportional to the weight of the car and dipends from the kind of tire and from the pressure that is inside (highter is the pressure lower is the friction).

2) a friction caused by the air. It is :
#F_r= rho xx S xx C_x xx v^2#
Where:
#rho# is the air density and is bigger when the Temperature is lower
S is the frontal surface of the car
Cx is the aerodinamical coefficient
v is the speed of the car.

At a speed over 30 km/h the second friction force is the main cause of the energy to give to keep the car cruising at a steady speed,

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